1. Field of the Invention
The present invention relates to an illumination apparatus, an image sensor unit, and an image reading apparatus.
2. Description of the Related Art
An image sensor unit and the like including a light source, a light guide, and the like are known. Patent Document 1 discloses an image sensor unit including a freely slidable light blocking member loosely inserted at a position covering a free end of the light guide in the longitudinal direction. In the image sensor unit of Patent Document 1, the light blocking member can block leak light directly emitted from between the free end of the light guide and the light source toward the original to thereby prevent the generation of leak light even if the light guide is expanded or contracted due to the ambient temperature or the like.
Patent Document 1
Japanese Laid-open Patent Publication 2012-142738
However, although the light blocking member of the image sensor unit can block the leak light emitted from the light source toward the original, the light incident on the light blocking member and directly reflected by the inner surface of the light blocking member may leak from the free end side. Particularly, the inner surface of the light blocking member is exposed when the light guide is contracted, compared to when the light guide is expanded. Therefore, more light is directly reflected to the inner surface of the light blocking member, and more leak light is generated. As a result, the leak light varies in response to the expansion and contraction of the light guide due to the ambient temperature, and making the illuminance on the original uniform is difficult.